The seasonal change in sign agrees with changes in the Sun-Earth distance. The present values of the ellipticity of the Earth’s orbit and the obliquity of its rotation axis lead to changes of orbital velocity with Summer in the southern hemisphere at perihelion and Summer in the northern hemisphere at aphelion. The torque associated with the Sun changes as velocity changes. As discussed in [1]}, [2]}, forces acting on the polar axis do so through a torque (\(m_1\) ,\( m_2\) ) obeying the Liouville-Euler system of equations (from blueLaplace, 1799). The influence of these torques is in quadrature with the length of day (lod). Changes in orbital velocity of our planet lead to a variation in the solar torque, which acts against the sense of rotation of the planet. Thus, annual variations in lod should be in opposition to changes in the Sun-Earth distance, and they are (Figure 8a, bottom). In the northern latitudes, both the Earth's rotation and the winds go from West to East, the Earth’s rotation slows in Summer and accelerates in Winter, hence positive pressure anomalies in Winter, negative in Summer. In other words, the pressure anomalies are due to the variation in rotation velocity (tracked through lod changes and winds). The phase difference between the annual components of lod and SLP is constant at 32 \(\pm \)  1.2 days (Figure 8b). Relative variations of amplitudes should be similar and indeed they are (Figure 8b).
